The disclosed embodiments relate to a method for the operative monitoring of track brakes for rail vehicles. Such a method is known from DE 101 55 143 A1.
Modern rail vehicles are usually equipped, in addition to a pneumatic brake system, with a magnetic track brake which is embodied as an eddy current brake or magnetic track brake.
In solid tracks, “suspension” is customary in which a brake magnet is held above the rails at a predetermined height of approximately 100 mm by springs. For the braking process, the spring forces are overcome by pneumatic activation cylinders, and the brake magnets are lowered onto the rail, into the work position, from the elevated position. At the same time, the brake is switched on electrically (cf. Wolfgang Hendrichs, “Das statische, dynamische and thermische Verhalten von Magnetschienenbremsen [The static, dynamic and thermal behavior of magnetic track brakes]”, Elektrische Bahnen [Electric Railways], eb, 86th year, issue July 1988, pp. 224-228).
In traction vehicles, it is also possible to provide a combination of elevated suspension and low suspension. The magnets are then suspended from pressure cylinders or air bellows which are pressed by means of compressed air into the elevated position against a centering stop which is fixed to the truck. When the brakes are activated, the pressure cylinders or air bellows are then are vented, the magnets being lowered into the standby position. In urban network vehicles such as, for example, trams, low suspension is customary. When a magnetic track brake is in the braking position, the brake magnet is generally in frictional contact with the rail.
In contrast, it is also the case that, in what is referred to as a linear eddy current brake, the brake magnet is held at a distance from the rail, electric solenoids magnetizing pole cores so that when an eddy current brake is switched on (and there is a relative movement of the eddy current brake with respect to the rail owing to the changes in the magnetic flux over time), eddy currents are induced in the travel rail. These eddy currents generate a secondary magnetic field which is opposed to the magnetic field of the eddy current brake. This results in a horizontal braking force which acts in opposition to the direction of travel. However, this requires there to be magnetic coupling between the rail and the brake magnet which depends essentially on the air gap between the brake magnet and the rail.
In both types of magnet brakes, the effectiveness of the brake is essentially on the respectively correct distance between the brake magnet and rail.
DE 101 55 143, therefore, proposes a diagnostic and monitoring device for monitoring the distance between the magnetic brake and the travel rail which uses a plurality of distance sensors which measure the air gap between the magnetic brake and the upper side of the rail. As a result, in both types of magnetic brakes it is possible to continuously check both whether the brake magnet is in the travel position and whether it is at the correct distance from the rail in the braking position.
However, the sensors require additional expenditure and there is the risk that, in the event of failure or malfunction of the sensors, faults are not detected or inappropriate fault signals are generated.
DE 100 09 331 C2 also proposes the use of sensors which measure the distance between the magnetic brake and the upper edge of the rail and, as a function of the measurement signal, open-loop/closed-loop control device which adjust the distance between the magnetic brake and the upper edge of the rail using actuators.